There are a few probable causes but before you tear up the tile and start over try this quick cracked grout fix.
How to fix cracked floor tile grout.
While grout may crack from wear and tear an uneven or weak subfloor.
A cup or bowl should work fine.
This will loosen any cracked and damaged grout.
Therefore learning how to repair cracked grout can be an essential skill to learn.
Dealing with cracked grout is a common issue that comes up for many homeowners at some point.
You can use a simple grout removal kit or i prefer using a dremel 568 grout removal kit which attaches to my dremel tool or the rockwell sonicrafter.
It is best to do this at an angle then smooth over the grout with a wet finger.
Repairing wide cracks in grout.
Remove all the loose and cracked grout with a grout saw or dremel tool and completely vacuum out the gaps.
In order to repair damaged grout that s cracking using new grout follow these steps.
Mix the new grout with water in a small container.
Use a bamboo skewer and drag it along the grout line.
Once the grout cracks for any reason it s time to repair broken grout before there is any damage to the surrounding tiles.
4 spread the grout and completely fill the cracks using a grout float.
Use a vacuum with a hose attachment to clean out any excess loosened grout.